Electrical terminal assembly and method of making same



June 11, 1968 R. s. SAUBER ELECTRICAL TERMINAL ASSEMBLY AND METHOD OF MAKING SAME Filed June 9, 1967 INVENTOR Rudolph S. Souber BY WITNESSES ATTORNEY United States Patent 3,388,368 ELECTRICAL TERMINAL ASSEMBLY AND METHOD OF MAKING SAME Rudolph S. Sauber, Greenville, Mich., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 9, 1967, Ser. No. 644,949 5 Claims. (Cl. 339-94) ABSTRACT OF THE DISCLOSURE An electrical terminal assembly for conducting electricity through a metallic wall of a hermetically sealed compressor in electrically insulated relation thereto, the assembly being formed of selected parts of uncured plastic assembled with conducting pins and other finished parts to the wall opening, and then cured in place so that the entire assembly is bonded together and hermetically seals the wall opening with the pins being held in electrically insulated relation to the wall.

Background of the invention Field of the invention-The invention relates generally to the art of electrical terminal assemblies, and particularly to those especially suited for use with hermetic compressors.

Description of the prior art.A commonly used and generally satisfactory terminal assembly for hermetic compressors is that shown in U.S. Patent No. 3,160,460. It essentially comprises a shallow, generally cup-shaped metal member carrying three conductor pins projecting through the base of the member, with the conductor pins being sealed to and electrically insulated from the cupshaped member by fused glass bushings surrounding the pins where they project through the member. This type terminal is seated in a single opening in the metallic wall of the motor compressor shell and sealed thereto by welding the periphery of the cup to the shell wall. Then the leads from the interior motor are then connected to the conductor pin portions projecting into the shell.

While as noted before these terminals generally perform satisfactorily, under certain operating conditions it has been found that the glass bushings about the conductor pins deteriorate in the refrigerant and oil environment within the shell. This deterioration is apparently promoted by the deposit of fine metallic particles on the exposed surfaces of the glass bushings which thereby provide a lowered resistance path for arcing and leakage of electricity from the terminal pins to the grounded cupshaped member and shell.

This invention avoids the use of the glass bushings which have been found to be subjected to deterioration, and also permits making a permanent and shielded connection of the motor leads to the conducting pins. Other advantages attributable to a structure according to this invention will appear from the following detailed description.

Summary of the invention In accordance with my invention, a sandwich-type assembly is built up in place on the shell wall and then treated to be bonded in place, hermetically seal the opening and hold the conductor pins in insulated relation to the wall. The sandwich-type assembly includes outer face disks of a stable insulating material on the opposite sides of the shell wall, inner wafers of solid form, uncured plastic abutting the opposite outer faces of the metallic shell, and center solid form, uncured plastic bushings seated in openings in the shell wall through which the conducting pins project. The wafers and disks are provided with openings to receive the conductor pins therethrough, these openings registering with center openings in the bushings seated in the wall. After the sandwich assembly is formed in place, it is heated to soften the uncured plastic elements so that they merge with each other to bond all of the parts together and hermetically seal the shell wall opening upon cooling.

It is to be noted that the method of forming the terminal by fabricating it and treating it in place, as distinguished from mounting a unitary completed terminal in place by welding, results in distinct advantages. The electric motor leads may be directly connected to the conductor pins so.that an intermediate connector between the leads and conductor pins is unnecessary. The parts of which the assembly are comprised are of a relatively simple and easily formed nature and accordingly are of low cost. The assembly is of a character that the parts exposed to the deleterious environment in the compressor shell are not adversely affected thereby.

Drawing description FIGURE 1 is a fragmentary, exploded isometric view illustrating the assembly parts in exploded relation;

FIG. 2 is a fragmentary elevation view of the inner 'face of the assembly in finished form;

Referring to FIG. 1 the curved side wall 10 of the hermetic compressor is provided with three equilaterally spaced holes 12 therein. Each of the holes receives a washer-shaped plastic bushing 14 having a thickness about the same as the shell wall and provided with a central hole 16. An uncured plastic wafer 13 provided with three small openings 20 disposed to register with the bushing central holes 16 abuts the inner face of the metallic shell Wall 10. An identical uncured plastic wafer 22 having holes 24 abuts the outer face of the shell Wall 10. As shown in the drawing, the diameters of the wafers 18 and 22 are adequate to more than encompass the area of the shell wall 10 in which the wall openings 12 are situated. Inner and outer phenolic material disks 26 and 28, respectively, also having equilaterally spaced holes 30 and 32 therein, overlie the inner and outer uncured plastic wafers 18 and 22.

Each conducting pin, which projects through a passage defined by the aligned openings in the parts described, comprises a solid outer portion 34, a shoulder 36, and a hollow sleeve inner portion 33. Each lead 40 from the motor (not shown) within the hermetic shell has a stripped end received in the hollow sleeve portion 38 of the conductor pin which is then being crimped. As shown in FIG. 3, the sleeve 38, shoulder 36 and the motor lead end portion are then coated with the uncured plastic material. This coating 42 may take various forms including that of a preformed hollow element which may be slid down over the connection after the motor lead is crimped in place.

The sequence of assembling the various parts to form the finished assembly of FIG. 4, may proceed as follows. The connection of each motor lead to its respective conductor pin (only one of three shown in FIG. 1) is made, and the cover 42 for the connection is applied. The inner disk 26, the inner wafer 18, and the three bushings 14 may then be slipped onto the outer portion 34 of the three conductor pins. This partial assembly may then be applied to the inner face of shell wall with the bushings 14 seating in the wall holes 12. The outer wafer 22 and the outer disk 28 are then slipped onto the outer portions 34 of the pins projecting outside the wall. The assembly is then heated in place to soften the uncured plastic and convert the material to a high strength, solvent resistant bond. When the assembly is then cooled, the parts are tightly bonded to each other and to the metallic wall 10. The softened material also fills any openings when it sets so that the assembly provides a hermetic seal between the inside and outside of the compressor shell in the area of the assembly.

One specific material from which the solid form uncured plastic parts may be fabricated is that sold by the 3M Company and identified as Scotch Weld AF111. This is a nonvolatile thermosetting adhesive which cures completely at 225 F.-250 F. in about an hour. In its uncured form it has a residual tackiness which facilitates holding the parts together for curing.

It will be appreciated that various modifications may be made within the scope of the invention. For example, While it is preferred that the terminal assembly be associated with a wall providing independent openings for each of the bushings 14 and the conductor pins which pass therethrough, a single wall opening can accommodate a conformingly-shaped single bushing provided with the requisite number of spaced holes for the conductors. However, the separate openings for each conductor in the shell wall 10 are preferred at present.

A terminal assembly according to the invention may also be used as a replacement assembly for that type of terminal earlier described as prior art. For replacement purposes, the terminal assembly according to this invention is' mounted on a separate metallic plate of substantially greater surface area than the area of the opening of the defective terminal assembly. The plate preferably should have a curvature conforming to that of the shell since a curved wall is more stable under pressure changes in the shell. Then the plate is simply welded about its periphery to the hermetic shell Wall as a patch over the original single opening. In this case of course, the conductor pins are not directly connected to the motor leads, and the inner portions 33 of the conductor pins are instead solid and of identical size to the inner pins of the terminal assembly being replaced.

I claim as my invention:

1. An electrical terminal assembly for conducting electricity through an opening in a metallic wall of a hermetically sealed device, said assembly comprising:

bushing means having a thickness substantially equal to said wall thiclmess disposed in said opening;

a pair of wafers abutting the inner and outer faces of said wall and circumscribing the area of said wall opening;

cover disks overlying both said inner and outer wafers;

a plurality of conductor pins of a length sufiicient to project away from the exposed faces of said cover disks;

each of said wafers, disks and bushing means including holes therein in alignment to receive said conductor pins therethrough, said holes being located to hold said pins in spaced relation from the edges of said metallic walls defining said opening;

said bushing means and said wafers being formed of solid form, uncured thermosetting material as as sembled, and then being heated to cure said thermosetting material and thereby bond said assembly together and to said wall and form a hermetic seal at said opening.

2. An assembly according to claim 1 wherein:

the inner end of each of said conductor pins is directly connected to an electrical lead, and a coating of said uncured material overlies said connection and the surfaces of said conductor pin exposed to the interior of said hermetically sealed device.

3. An assembly according to claim 1 wherein:

said opening in said metallic wall comprises a number of individual, separate openings, each of which accommodates a separate portion of said bushing means and a conductor pin.

4. An assembly according to claim 2 wherein:

each of said conductor pins includes an inner portion with a shoulder thereon adapted to abut the inner cover disk, said inner portion comprising a hollow sleeve receiving said lead, said shoulder and said inner portion being coated with said uncured material.

5. The method of making a multi-pin terminal assembly bonded in place to a metallic wall through which electricity is to be conducted in insulated relation, comprising the steps of:

installing an uncured plastic bushing in each opening in said metallic wall through which a terminal pin is to extend, each bushing including a central open ing for its respective pin substantially occupying the remainder of said metallic wall opening;

placing a wafer of uncured thermosetting material against each face of said metallic wall, each wafer including apertures registering with said bushing central openings, and having a periphery circumscribing the area of said wall containing said wall openings; placing a disk of electrically insulating material in overlying relation to the outer face of each of said wafers, said disks including apertures registering with said wafer apertures; inserting a conducting pin through each passage formed by the registering apertures in said first and second wafer-shaped disks and said bushings; and

then, heating said assembly to cure said uncured material parts and thereby bond said assembly directly directly to said metallic wall in hermetically sealing relation, with said pins being held in insulated relation from said metallic wall.

References Cited UNITED STATES PATENTS 2,582,931 1/1952 Kodama 339-218 X 2,666,805 1/ 1954- Smith 339-94 X 2,757,355 7/1956 Howes et a1. 33994 X 3,334,395 8/1967 Cook et al. 29-625 FOREIGN PATENTS 546,849 3/1932 Germany. 190,778 12/1922 Great Britain.

RICHARD E. MOORE, Primary Examiner. 

